Method and apparatus for performing backoff for scheduling request in wireless communication system

ABSTRACT

A method and apparatus for scheduling uplink (UL) transmission in a wireless communication system is provided. A user equipment (UE) receives a backoff parameter from a network, and determines whether or not to apply the received backoff parameter before transmitting a scheduling request (SR) to the network via a dedicated channel. Whether or not to apply the received backoff parameter is determined according to a prioritized access, and the prioritized access corresponds to one of emergency access, high priority access, control element/information in media access control (MAC), radio link control (RLC) or packet data convergence protocol (PDCP), data radio bearer (DRB) for voice/video service, signaling radio bearer (SRB) 0, SRB 1, SRB 2, multimedia telephony service (MMTEL)-voice, MMTEL-video, and voice over long-term evolution (VoLTE).

This is a Continuation Application of U.S. patent application Ser. No.14/433,491 filed Apr. 3, 2015, which is a 35 U.S.C. § 371 National Stageentry of International Application No. PCT/KR2013/009483, filed Oct. 23,2013, which claims benefit of Provisional Application No. 61/717,616filed Oct. 23, 2012, both of which are incorporated by reference intheir entirety herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for performing backoff for ascheduling request in a wireless communication system.

Related Art

Universal mobile telecommunications system (UMTS) is a 3rd generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

In 3GPP LTE, a scheduling request (SR) is used for requesting uplinkshared channel (UL-SCH) resources for new transmission. For example, ifa user equipment (UE) does not have allocated uplink radio resourceswhen a buffer status report (BSR) is triggered, the UE performs a SRprocedure for receiving uplink radio resources from a BS. The UE maytransmit the trigger BSR using the allocated uplink radio resources bythe SR procedure.

Meanwhile, backoff may be performed for a random access procedure.Backoff means that transmission of a random access preamble is delayedif a random access response reception and/or contention resolution inthe random access procedure is considered not successful.

Currently, backoff is not performed for the SR. However, a method forperforming backoff for the SR may be considered.

SUMMARY OF THE INVENTION

The present invention provides a method for performing backoff for ascheduling request (SR) in a wireless communication system. The presentinvention provides a method for determining whether to apply a backoffparameter before transmitting an SR.

In an aspect, a method for scheduling uplink (UL) transmission in awireless communication system is provided. The method includes receivinga backoff parameter from a network, and determining whether or not toapply the received backoff parameter before transmitting a schedulingrequest (SR) to the network via a dedicated channel.

Whether or not to apply the received backoff parameter may be determinedaccording to a prioritized access.

The prioritized access may correspond to one of emergency access, highpriority access, control element/information in media access control(MAC), radio link control (RLC) or packet data convergence protocol(PDCP), data radio bearer (DRB) for voice/video service, signaling radiobearer (SRB) 0, SRB 1, SRB 2, multimedia telephony service(MMTEL)-voice, MMTEL-video, and voice over long-term evolution (VoLTE).

It may be determined to apply the received backoff parameter if theprioritized access is not identified. The method may further includeperforming backoff based on the received backoff parameter beforetransmitting the SR to the network.

It may be determined not to apply the received backoff parameter if theprioritized access is identified. The method may further includeignoring the received backoff parameter before transmitting the SR tothe network.

The method may further include receiving a backoff configuration fromthe network via one of system information, a paging, and a radioresource control (RRC) connection reconfiguration message. The backoffconfiguration may include the backoff parameter.

The method may further include transmitting the SR to the network viathe dedicated channel.

In another aspect, a user equipment (UE) in a wireless communicationsystem is provided. The UE includes a radio frequency (RF) unit fortransmitting or receiving a radio signal, and a processor coupled to theRF unit, and configured to receive a backoff parameter from a network,and determine whether or not to apply the received backoff parameterbefore transmitting a scheduling request (SR) to the network via adedicated channel.

Important access trials can avoid blocking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of a wireless communication system.

FIG. 2 is a diagram showing radio interface protocol architecture for acontrol plane.

FIG. 3 is a diagram showing radio interface protocol architecture for auser plane.

FIG. 4 shows an example of a physical channel structure.

FIG. 5 shows an example of a scheduling request procedure.

FIG. 6 shows an example of a method for scheduling UL transmissionaccording to an embodiment of the present invention.

FIG. 7 shows another example of a method for scheduling UL transmissionaccording to an embodiment of the present invention.

FIG. 8 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is evolved from IEEE 802.16e, and provides backwardcompatibility with a system based on the IEEE 802.16e. The UTRA is apart of a universal mobile telecommunication system (UMTS). 3rdgeneration partnership project (3GPP) long term evolution (LTE) is apart of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses theOFDMA in a downlink and uses the SC-FDMA in an uplink. LTE-advanced(LTE-A) is an evolution of the LTE.

For clarity, the following description will focus on LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 1 shows a structure of a wireless communication system.

The structure of FIG. 1 is an example of a network structure of anevolved-UMTS terrestrial radio access network (E-UTRAN). An E-UTRANsystem may be a 3GPP LTE/LTE-A system. An evolved-UMTS includes a userequipment (UE) 10 and a base station (BS) 20 which provides a controlplane and a user plane to the UE. The user equipment (UE) 10 may befixed or mobile, and may be referred to as another terminology, such asa mobile station (MS), a user terminal (UT), a subscriber station (SS),a wireless device, etc. The BS 20 may be generally a fixed station thatcommunicates with the UE 10 and may be referred to as anotherterminology, such as an evolved node-B (eNB), a base transceiver system(BTS), an access point, etc. There may be one or more cells within thecoverage of the BS 20. A single cell may be configured to have one ofbandwidths selected from 1.25, 2.5, 5, 10, and 20 MHz, etc., and mayprovide downlink or uplink transmission services to several UEs. In thiscase, different cells may be configured to provide different bandwidths.

Interfaces for transmitting user traffic or control traffic may be usedbetween the BSs 20. The UE 10 and the BS 20 may be connected by means ofa Uu interface. The BSs 20 may be interconnected by means of an X2interface. The BSs 20 may be connected to an evolved packet core (EPC)by means of an S1 interface. The EPC may consist of a mobilitymanagement entity (MME), a serving gateway (S-GW), and a packet datanetwork (PDN) gateway (PDN-GW). The MME has UE access information or UEcapability information, and such information may be primarily used in UEmobility management. The S-GW is a gateway of which an endpoint is anE-UTRAN. The PDN-GW is a gateway of which an endpoint is a PDN. The MMEis in charge of functionality of a control plane. The S-GW is in chargeof functionality of a user plane. The BSs 20 may be connected to the MME30 by means of an S1-MME interface, and may be connected to the S-GW bymeans of an S1-U interface. The S1 interface supports a many-to-manyrelation between the BS 20 and the MME/S-GW 30.

Hereinafter, a downlink (DL) denotes communication from the BS 20 to theUE 10, and an uplink (UL) denotes communication from the UE 10 to the BS20. In the DL, a transmitter may be a part of the BS 20, and a receivermay be a part of the UE 10. In the UL, the transmitter may be a part ofthe UE 10, and the receiver may be a part of the BS 20.

FIG. 2 is a diagram showing radio interface protocol architecture for acontrol plane. FIG. 3 is a diagram showing radio interface protocolarchitecture for a user plane.

Layers of a radio interface protocol between the UE and the E-UTRAN areclassified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. The radio interface protocol between the UE and the E-UTRAN maybe horizontally divided into a physical layer, a data link layer, and anetwork layer, and may be vertically divided into a control plane whichis a protocol stack for control signal transmission and a user planewhich is a protocol stack for data information transmission. The layersof the radio interface protocol may exist in pairs at the UE and theE-UTRAN.

A physical (PHY) layer belonging to the L1 provides an upper layer withan information transfer service through a physical channel. The PHYlayer is connected to a medium access control (MAC) layer which is anupper layer of the PHY layer through a transport channel. Data may betransferred between the MAC layer and the PHY layer through thetransport channel. The transport channel may be classified according tohow and with what characteristics data is transmitted through a radiointerface. Or, the transport channel may be classified into a dedicatedtransport channel and a common transport channel depending on whether ornot to share the transport channel. Between different PHY layers, i.e.,a PHY layer of a transmitter and a PHY layer of a receiver, data may betransferred through the physical channel. The physical channel may bemodulated using an orthogonal frequency division multiplexing (OFDM)scheme, and utilizes time and frequency as a radio resource.

FIG. 4 shows an example of a physical channel structure.

A physical channel may consist of a plurality of subframes in a timedomain and a plurality of subcarriers in a frequency domain. Onesubframe may consist of a plurality of symbols in the time domain. Onesubframe may consist of a plurality of resource blocks (RBs). One RB mayconsist of a plurality of symbols and a plurality of subcarriers. Inaddition, each subframe may use specific subcarriers of specific symbolsof a corresponding subframe for a physical downlink control channel(PDCCH). For example, a first symbol of the subframe may be used for thePDCCH. A transmission time interval (TTI) which is a unit time for datatransmission may be equal to a length of one subframe.

A MAC layer belonging to the L2 provides a service to a higher layer,i.e., a radio link control (RLC), through a logical channel. A functionof the MAC layer includes mapping between logical channels and transportchannels and multiplexing/de-multiplexing for a transport block providedto a physical channel on a transport channel of a MAC service data unit(SDU) belonging to the logical channels. The logical channels arelocated above the transport channels, and are mapped to the transportchannels. The logical channels may be divided into control channels fordelivering information of the control plane and traffic channels fordelivering information of the user plane.

An RLC layer belonging to the L2 supports reliable data transmission. Afunction of the RLC layer includes RLC SDU concatenation, segmentation,and reassembly. To ensure a variety of quality of service (QoS) requiredby a radio bearer (RB), the RLC layer provides three operation modes,i.e., a transparent mode (TM), an unacknowledged mode (UM), and anacknowledged mode (AM). The AM RLC provides error correction by using anautomatic repeat request (ARQ). Meanwhile, a function of the RLC layercan be implemented with a functional block inside the MAC layer. In thiscase, the RLC layer may not exist.

A packet data convergence protocol (PDCP) layer belongs to the L2. Afunction of a packet data convergence protocol (PDCP) layer in the userplane includes user data delivery, header compression, and ciphering.The header compression has a function for decreasing a size of an IPpacket header which contains relatively large-sized and unnecessarycontrol information, to support effective transmission in a radiosection having a narrow bandwidth. A function of a PDCP layer in thecontrol plane includes control-plane data delivery andciphering/integrity protection.

A radio resource control (RRC) layer belonging to the L3 is defined onlyin the control plane. The RRC layer takes a role of controlling a radioresource between the UE and the network. For this, the UE and thenetwork exchange an RRC message through the RRC layer. The RRC layerserves to control the logical channel, the transport channel, and thephysical channel in association with configuration, reconfiguration, andrelease of RBs. An RB is a logical path provided by the L2 for datadelivery between the UE and the network. The configuration of the RBimplies a process for specifying a radio protocol layer and channelproperties to provide a particular service and for determiningrespective detailed parameters and operations. The RB can be classifiedinto two types, i.e., a signaling RB (SRB) and a data RB (DRB). The SRBis used as a path for transmitting an RRC message in the control plane.The DRB is used as a path for transmitting user data in the user plane.

An RRC state indicates whether an RRC of a user equipment (UE) islogically connected to an RRC of an E-UTRAN. When an RRC connection isestablished between an RRC layer of the UE and an RRC layer of theE-UTRAN, the UE is in an RRC connected state (RRC_CONNECTED), andotherwise the UE is in an RRC idle state (RRC_IDLE). Since the UE inRRC_CONNECTED has the RRC connection established with the E-UTRAN, theE-UTRAN can recognize the existence of the UE in RRC_CONNECTED and caneffectively control the UE. Meanwhile, the UE in RRC_IDLE cannot berecognized by the E-UTRAN, and a core network (CN) manages the UE inunit of a tracking area (TA) which is a larger area than a cell. Thatis, only the existence of the UE in RRC_IDLE is recognized in unit of alarge area, and the UE must transition to RRC_CONNECTED to receive atypical mobile communication service such as voice or datacommunication.

When the user initially powers on the UE, the UE first searches for aproper cell and then remains in RRC_IDLE in the cell. When there is aneed to establish an RRC connection, the UE which remains in RRC_IDLEmay establish the RRC connection with the RRC of the E-UTRAN through anRRC connection procedure and then may transition to RRC_CONNECTED. TheUE which remains in RRC_IDLE may need to establish the RRC connectionwith the E-UTRAN when uplink data transmission is necessary due to auser's call attempt or the like or when there is a need to transmit aresponse message upon receiving a paging message from the E-UTRAN.

A scheduling request (SR) is described below. It may be referred toSection 5.4.4 of 3GPP TS 36.321 V9.1.0 (2009-12).

An SR is used for requesting UL-SCH resources for new transmission.

When an SR is triggered, it may be considered as pending until it iscancelled. All pending SR(s) may be cancelled and sr-ProhibitTimer maybe stopped when a MAC PDU is assembled and this PDU includes a BSR whichcontains buffer status up to (and including) the last event thattriggered a BSR, or when the UL grant(s) can accommodate all pendingdata available for transmission.

If an SR is triggered and there is no other SR pending, the UE may setthe SR_COUNTER to 0.

As long as one SR is pending, the UE shall for each TTI:

if no UL-SCH resources are available for a transmission in this TTI:

-   -   if the UE has no valid PUCCH resource for SR configured in any        TTI: initiate a random access procedure and cancel all pending        SRs;    -   else if the UE has a valid PUCCH resource for SR configured for        this TTI and if this TTI is not part of a measurement gap and if        sr-ProhibitTimer is not running:        -   if SR_COUNTER<dsr-TransMax:            -   increment SR_COUNTER by 1;            -   instruct a physical layer to signal the SR on PUCCH;            -   start the sr-ProhibitTimer.        -   else:            -   notify RRC to release PUCCH/SRS;            -   clear any configured downlink assignments and uplink                grants;            -   initiate a random access procedure and cancel all                pending SRs.

FIG. 5 shows an example of a scheduling request procedure.

Referring to FIG. 5, a method for performing an SR procedure through adedicated scheduling request (D-SR) channel is described. A BS allocatesD-SR channels, having regular intervals, to a UE. If UL data arrives,the UE triggers a buffer status reporting (BSR). If the UE does not haveallocated radio resources, the UE triggers an SR. After, the UE performsan SR procedure through the D-SR channels. Upon receiving the SR fromthe UE, the BS determines resource distribution and informs the UEallocated uplink radio resources to the UE through a PDCCH according toa scheduling algorithm. If the D-SR channels are not allocated to theUE, the UE performs an SR procedure through a random access procedure.

A buffer status reporting (BSR) is described below. It may be referredto Section 5.4.5 of 3GPP TS 36.321 V9.1.0 (2009-12).

A BSR procedure is used to provide a serving eNB with information aboutan amount of data available for transmission in UL buffers of a UE. AnRRC may control the BSR reporting by configuring two timersperiodicBSR-Timer and retxBSR-Timer and by, for each logical channel,optionally signaling logicalChannelGroup which allocates the logicalchannel to a logical channel group (LCG).

For the BSR procedure, the UE may consider all radio bearers which arenot suspended and may consider radio bearers which are suspended.

The BSR procedure may be triggered if any of the following events occur:

UL data, for a logical channel which belongs to a LCG, becomes availablefor transmission in an RLC entity or in an PDCP entity, and either thedata belongs to a logical channel with higher priority than prioritiesof logical channels which belong to any LCG and for which data isalready available for transmission, or there is no data available fortransmission for any of logical channels which belong to a LCG, in whichcase the BSR is referred below to as “regular BSR”;

UL resources are allocated and number of padding bits is equal to orlarger than a size of a BSR MAC control element (CE) plus its subheader,in which case the BSR is referred below to as “padding BSR”;

retxBSR-Timer expires and the UE has data available for transmission forany of logical channels which belong to a LCG, in which case the BSR isreferred below to as “regular BSR”;

periodicBSR-Timer expires, in which case the BSR is referred below to as“periodic BSR”.

For the regular BSR and the periodic BSR:

if more than one LCG has data available for transmission in the TTIwhere the BSR is transmitted: report a long BSR;

else report a short BSR.

For the padding BSR:

if the number of padding bits is equal to or larger than a size of ashort BSR plus its subheader but smaller than a size of a long BSR plusits subheader:

-   -   if more than one LCG has data available for transmission in the        TTI where the BSR is transmitted: report a truncated BSR of the        LCG with the highest priority logical channel with data        available for transmission;    -   else report a short BSR.

else if the number of padding bits is equal to or larger than a size ofa long BSR plus its subheader, report a long BSR.

If the BSR procedure determines that at least one BSR has been triggeredand not cancelled:

if the UE has UL resources allocated for new transmission for this TTI:

-   -   instruct multiplexing and assembly procedure to generate the BSR        MAC CE(s);    -   start or restart periodicBSR-Timer except when all the generated        BSRs are truncated BSRs;    -   start or restart retxBSR-Timer.

else if a regular BSR has been triggered:

-   -   if an uplink grant is not configured or the regular BSR was not        triggered due to data becoming available for transmission for a        logical channel for which logical channel SR masking        (logicalChannelSR-Mask) is setup by upper layers:        -   a scheduling request shall be triggered.

A MAC PDU may contain at most one MAC BSR CE, even when multiple eventstrigger a BSR by the time a BSR can be transmitted in which case theregular BSR and the periodic BSR shall have precedence over the paddingBSR.

The UE may restart retxBSR-Timer upon indication of a grant fortransmission of new data on any UL-SCH.

All triggered BSRs may be cancelled in case the UL grant(s) in thissubframe can accommodate all pending data available for transmission butis not sufficient to additionally accommodate the BSR MAC CE plus itssubheader. All triggered BSRs may be cancelled when a BSR is included ina MAC PDU for transmission.

The UE may transmit at most one regular/periodic BSR in a TTI. If the UEis requested to transmit multiple MAC PDUs in a TTI, it may include apadding BSR in any of the MAC PDUs which do not contain aregular/periodic BSR.

All BSRs transmitted in a TTI may always reflect a buffer status afterall MAC PDUs have been built for this TTI. Each LCG may report at themost one buffer status value per TTI and this value may be reported inall BSRs reporting buffer status for this LCG.

In a random access procedure, backoff may be performed. In detail, in arandom access procedure initialization, a backoff parameter value in theUE is set to 0 ms. In random access response reception, the UE may stopmonitoring for random access response(s) after successful reception ofthe random access response containing random access preamble identifiersthat matches the transmitted random access preamble. In this case, ifthe random access response contains a backoff indicator (BI) subheader,the backoff parameter value in the UE is set as indicated by a BI fieldof the BI subheader. Else, the backoff parameter value in the UE is setto 0 ms.

The backoff parameter values may be presented by Table 1.

TABLE 1 Backoff Parameter value Index (ms) 0 0 1 10 2 20 3 30 4 40 5 606 80 7 120 8 160 9 240 10 320 11 480 12 960 13 Reserved 14 Reserved 15Reserved

The reserved values of the backoff parameter if received by the currentrelease version UEs shall be taken as 960 ms.

If no random access response is received within the random accessresponse window, or if none of all received random access responsescontains a random access preamble identifier corresponding to thetransmitted random access preamble, the random access response receptionis considered not successful. In this case, the UE selects a randombackoff time according to a uniform distribution between 0 and thepackoff parameter value based on the backoff parameter in the UE, anddelays the subsequent random access transmission by the backoff time.

Or, in contention resolution, if the contention resolution is considerednot successful, the UE selects a random backoff time according to auniform distribution between 0 and the backoff parameter value based onbased on the backoff parameter in the UE, and delays the subsequentrandom access transmission by the backoff time.

When uplink congestion occurs at a cell, important access trials as wellas normal access trials can be blocked. Currently, backoff is notperformed for the SR. However, a method for performing backoff for theSR may be considered for prioritizing an SR for important access trials.Accordingly, a method for performing backoff for an SR may be proposed.

FIG. 6 shows an example of a method for scheduling UL transmissionaccording to an embodiment of the present invention.

At step S100, the UE receives a backoff parameter from a network. Atstep S110, the UE determines whether or not to apply the receivedbackoff parameter before transmitting an SR to the network via adedicated channel.

Whether or not to apply the received backoff parameter may be determinedaccording to a prioritized access. The prioritized access may correspondto a logical channel, traffic/bearer type, or logical channel priorityincluding one of emergency access, high priority access, controlelement/information in media access control (MAC), radio link control(RLC) or packet data convergence protocol (PDCP), data radio bearer(DRB) for voice/video service, signaling radio bearer (SRB) 0, SRB 1,SRB 2, multimedia telephony service (MMTEL)-voice, MMTEL-video, andvoice over long-term evolution (VoLTE). If the prioritized access isidentified, it is determined not to apply the received backoff parameterfor an SR. That is, the UE ignores the received backoff parameter beforetransmitting the SR to the network, according to the prior art. On theother hand, if the prioritized access is not identified, it isdetermined to apply the received backoff parameter for an SR. That is,the UE performs backoff based on the received backoff parameter beforetransmitting the SR to the network, according to an embodiment of thepresent invention.

FIG. 7 shows another example of a method for scheduling UL transmissionaccording to an embodiment of the present invention.

At step S200, for an SR via a PUCCH, the UE receives a backoffconfiguration via system information, paging, or UE dedicated RRCmessage, such as an RRC connection reconfiguration message. If thesystem information is used to carry the backoff configuration, thepaging may be used to indicate whether or not the backoff configurationis carried in the system information.

The backoff configuration may indicate whether or not this cell supportsperforming backoff for an SR according to the embodiment of the presentinvention. That is, only if the backoff configuration indicates thatthis cell supports performing backoff for an SR according to theembodiment of the present invention, the UE can perform backoff for anSR accordring to the embodiment of the present invention. Otherwise, theUE does not perform backoff before transmitting an SR according to theprior art.

In addition, the backoff configuration can inform UEs for whichestablishment cause or traffic/bearer type UEs ignore backoff or apply aspecial backoff parameter before (re-)transmitting an SR when UEs needto perform backoff. For instance, the backoff configuration can indicateone or some of emergency access, high priority access, MMTEL-voice,MMTEL-video, and VoLTE. If the UE receives this backoff configuration,and if the UE has accessed for one of the indicated ones, the UE ignoresbackoff before transmitting an SR or applies a special backoff parameterbefore transmitting an SR.

Alternatively, the backoff configuration can indicate one or some ofmobile originating (MO)-data, mobile terminating (MT) access,MMTEL-other, and data service. If the UE receives this backoffconfiguration, and if the UE has accessed for one of the indicated ones,the UE applies backoff before transmitting an SR.

Otherwise, the UE ignores backoff or applies a special backoff parameterbefore transmitting an SR.

The special backoff parameter may be provided via a random accessresponse, system information, or UE dedicated RRC message.

At step S210, the UE triggers an SR procedure. The UE may receive thebackoff information via a random access response, paging, systeminformation or UE dedicated message, and then store the received backoffinformation. If the system information is used to carry the backoffinformation, the paging can be used to indicate whether or not thebackoff information is carried in the system information.

At step S220, upon triggering the SR procedure, the UE decides whetheror not to perform backoff before transmitting an SR based on thereceived backoff information. The received backoff information includesat least the backoff parameter. It is assumed that the UE receives thebackoff parameter.

If the UE in RRC_CONNECTED has established this RRC connection for anestablishment cause set to one of ‘emergency access’ and ‘high priorityaccess’; or,

if the UE in RRC_CONNECTED has established this RRC connection for oneor some of emergency access, high priority access, MMTEL-voice,MMTEL-video, and VoLTE; or,

if the UE has established bearers for one or some of emergency access,high priority access, MMTEL-voice, MMTEL-video, and VoLTE; or

if the UE initiates this SR to transmit a buffer status report for aspecific logical channel, a specific logical channel group, or asignaling radio bearer (and if the specific logical channel or thespecific logical channel group is indicated via system information,paging, or random access response); or

if the UE initiates this SR to transmit MAC control element or controlinformation in RLC/PDCP; or

if the UE initiates this SR to transmit a NAS message or RRC message,

the UE ignores the received backoff parameter and transmits the SRwithout backoff. Or, if the UE receives the existing backoff parameterin a random access response, and if the backoff parameter has a largervalue than 960 ms, the UE applies backoff with 960 ms and then transmitsthe SR after backoff. But, if the backoff parameter value is 960 ms orless, the UE applies backoff with the value and then transmits the SRafter backoff. Or, if the UE receives the special backoff parameter, theUE applies backoff and then transmits the SR after backoff.

Else, the UE applies the (existing) backoff parameter and then transmitsthe SR after backoff.

If the UE does not receive the backoff parameter, the UE transmits theSR without backoff.

At step S230, the UE transmits the SR on the PUCCH with or withoutbackoff according to the previous steps.

At step S240, in response to the SR, the eNB may respond by transmittinga UL grant to the UE on a PDCCH.

FIG. 8 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

ABS 800 may include a processor 810, a memory 820 and a radio frequency(RF) unit 830. The processor 810 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 810. The memory 820 is operatively coupled with the processor810 and stores a variety of information to operate the processor 810.The RF unit 830 is operatively coupled with the processor 810, andtransmits and/or receives a radio signal.

A UE 900 may include a processor 910, a memory 920 and a RF unit 930.The processor 910 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 910. Thememory 920 is operatively coupled with the processor 910 and stores avariety of information to operate the processor 910. The RF unit 930 isoperatively coupled with the processor 910, and transmits and/orreceives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The RF units 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method for scheduling uplink (UL) transmissionin a wireless communication system, the method comprising: receiving, bya User Equipment (UE), a backoff parameter from a network via a radioresource control (RRC) message, wherein the backoff parameter relates toa transmission of a scheduling request (SR); determining, by the UE,whether or not to apply the received backoff parameter beforetransmitting the SR to the network via a dedicated channel; when it isdetermined that the received backoff parameter applies, transmitting, bythe UE, the SR to the network via the dedicated channel according to thereceived backoff parameter; and wherein the backoff parameter isconfigured for a specific logical channel.
 2. The method of claim 1,wherein determining whether or not to apply the received backoffparameter is based on a prioritized access.
 3. The method of claim 2,wherein the prioritized access corresponds to one of emergency access,high priority access, control element/information in media accesscontrol (MAC), radio link control (RLC) or packet data convergenceprotocol (PDCP), data radio bearer (DRB) for voice/video service,signaling radio bearer (SRB) 0, SRB 1, SRB 2, multimedia telephonyservice (MMTEL)-voice, MMTEL-video, and voice over long-term evolution(VoLTE).
 4. The method of claim 2, wherein the received backoffparameter is not applied when the prioritized access is not identified.5. The method of claim 4, further comprising: performing backoff basedon the received backoff parameter before transmitting the SR to thenetwork.
 6. The method of claim 2, wherein the received backoffparameter is applied when the prioritized access is identified.
 7. Themethod of claim 6, further comprising: when it is determined that thereceived backoff parameter is not applied, transmitting, by the UE, theSR to the network via the dedicated channel without delaying thetransmission of the SR.
 8. The method of claim 1, wherein the receivedbackoff parameter relates to a value for a SR prohibit timer, and thevalue for the SR prohibit timer is configured by an upper layer.
 9. Themethod of claim 8, wherein the value for the SR prohibit timer is usedto indicate a time for delaying the transmission of the SR in units ofsubframes.
 10. The method of claim 1, wherein the backoff parameter isconfigured by an upper layer.
 11. A user equipment (UE) in a wirelesscommunication system, the UE comprising: a transmitter and receiver; anda processor, coupled to the transmitter and receiver, that: controls thereceiver to receive a backoff parameter from a network via a radioresource control (RRC) message, wherein the backoff parameter relates toa transmission of a scheduling request (SR); and determines whether ornot to apply the received backoff parameter before the SR is transmittedto the network via a dedicated channel; when it is determined that thereceived backoff parameter applies, controlling the transmitter totransmit the SR to the network via the dedicated channel according tothe received backoff parameter; and wherein the backoff parameter isconfigured for a specific logical channel.
 12. The UE of claim 11,wherein the processor further determines whether or not to apply thereceived backoff parameter based on a prioritized access.
 13. The UE ofclaim 12, wherein the prioritized access corresponds to one of emergencyaccess, high priority access, control element/information in mediaaccess control (MAC), radio link control (RLC) or packet dataconvergence protocol (PDCP), data radio bearer (DRB) for voice/videoservice, signaling radio bearer (SRB) 0, SRB 1, SRB 2, multimediatelephony service (MMTEL)-voice, MMTEL-video, and voice over long-termevolution (VoLTE).
 14. The UE of claim 12, wherein the processordetermines to apply the received backoff parameter when the prioritizedaccess is not identified.
 15. The UE of claim 12, wherein the processordetermines to apply the received backoff parameter when the prioritizedaccess is not identified.